Compressor



Feb. 4, 1964 K. H. RHODES 3,120,338

COMPRESSOR Filed Sept. 17, 1962 United States Patent 3,120,333 COMPRESSUR Keith H. Rhodes, Racine, Wis., assignor to Walker Manufacturing tjompany, Racine, Win, a corporation of Delaware Filed 591st. 17, 1962, Ser. No. 224,168 2 Cl. (Cl. 230-58) This invention relates generally to air compressors and more particularly to an improved positive displacement double-acting air compressor.

Conventional positive displacement air compressors generally comprise a piston that is driven by a crankshaft through an articulated connecting rod. The piston in movable in translation within a complementary cylinder, eccentricity of the crankshaft being accommodated by articulation of the connecting rod.

The air compressor of the instant invention features a shuttle piston, that is molded from nylon or a fluorocarbon, having a laterally extending groove for the direct acceptance of a crank pin, thereby eliminating the conventional connecting rod and wrist pin assemblies, as well as the problems attendant to manufacture and assembly of the rod, wrist pin, and piston.

Accordingly, one object of the instant invention is an improved air compressor.

Another object of the instant invention is an air compressor having a double-acting shuttle piston.

Another object of the instant invention is an air compressor having a piston molded from nylon or a fluoro carbon.

Another object is an air compressor that eliminates the conventional wrist pin and connecting rod assembly.

Other objects and advantages of the instant invention will be apparent in the following specification, claims and drawings, wherein:

FIGURE 1 is a side view of an air compressor in accordance with an exemplary embodiment of the instant invention shown in operative association with a conventional electric motor;

lFIG. 2 is a view taken in the direction of the arrow 2 in FIG. 1;

FIG. 3 is a cross-sectional view taken substantially along the line 33 of FIG. 1;

FIG. 4 is a cross-sectional View taken substantially along the line 44 of FIG. 3;

FIG. 5 is a cross-sectional view taken substantially along the line 55 of FIG. 3; and

FIG. 6 is a cross-sectional view taken substantially along the line 66 of FIG. 3 with the flapper and disc valves in the intake condition.

As best seen in FIG. 1 of the drawings, an air compressor 1%, in accordance with an exemplary embodiment of the instant invention is shown in operative association with an electric motor 12. The air compressor 19- is secured to the motor 12 as by a pair of mounting bolts 14 and 16 having complementary nuts 18 and 19', respectively.

The air compressor comprises a crank housing 20, preferably a steel stamping, having a pair of radially extending flanges 22 and 24 with apertures (not shown) for the acceptance of the mounting bolts 14 and 16 on the motor 12, respectively. The housing 20 is of tubular construction having an inside diameter complementary to a bearing housing 3t) of the motor 12 for the acceptance thereof in slidable press fit relationship.

A cylinder 40, of circular cross section, is secured to the housing 20, as by brazing, for the acceptance of a shuttle piston 42.

The piston 42 is molded from, for example, nylon or fluorocarbon, and has opposite end portions 44 and 46 of 3,12%,333 Patented Feb. 4, 1964 like construction so as to function as a double-acting shuttle piston. The end portions 44 and 46 of the piston 42 have cylinder contacting annular surfaces 48 and 5% respectively, that are maintained in intimate sealing con tact with an inner surface 52 of the cylinder 40 due to air pressure acting on annular flanges 54 and 56 on the end portions 44 and 46. The flanges 54 and 56 are defined by recesses 58 and 61 in the end portions 44 and 46 of the piston 42, respectively.

A center portion 62 of the piston 42 has a lateral groove 64 therein for the acceptance of a crank pin 66. It is to be noted that the crank pin 66 is secured directly to an output shaft 63 of the motor 12 by a machine screw 79' that extends through a complementary bore 71 in the output shaft 68 and which has a threaded end portion 72 which is accepted in a complementary threaded bore 74 in the crank pin 66. It is also to be noted that a head portion 76 of the machine screw 80 is of relatively large diameter and axial dimension thereby to function as a counterweight for the crank pin 66 to statically balance the crank pin 66 and the piston assembly 42.

The crank pin 66 moves within the lateral groove 64 in the piston 42 upon rotation about the output shaft 68 to effect reciprocation of the piston 42 in the manner of a Scotch yoke assembly.

As best seen in FIGS. 2 and 3, a spring clip 84 is disposed about the cylinder iil, end portions 86 and 88 thereof extending through the cylinder 40 to engage a complementary flat 90 on the piston 42 to preclude rotation thereof about its longitudinal axis.

As best seen in FIGS. 3 and 6, a pair of valve assemblies of like construction and generally designated by the numeral 94 are sealably retained on opposite ends 96 and 98 of the cylinder at Each valve assembly 94 comprises a tubular valve housing 100 having a pair of diametrically related flanges 102 and 1M thereon to facilitate attachment of the housing 1% to an annular valve plate 1%. The valve plate 196 is secured to the cylinder 40 by a plurality of folded tabs 107, 108, and 102 thereon (FIG. 2).

A sleeve 116 is disposed interiorly of the valve housing 105 to function as a stop for a generally rectangular disc valve 112 made from, for example, nylon. The disc valve 112 is seated alternatively against the valve disc 106 to close a central aperture 113 therein and against an annular end face 114 of the sleeve 116. The sleeve 11% has a plurality of circumferentially spaced apertures 116 therein for the passage of air outwardly of the valve housing 109 when the valve 112 is seated against the seat 114 on the sleeve 1111, as will be described.

An annular flapper valve 120, preferably made from nylon, and having a central aperture 121, is retained against the valve plate 1% by a pair of rivets 122 and 124 that extend through complementary spacers 126 and 123, respectively. The flapper valve normally closes a pair of apertures 130 and 132 (FIGS. 2 and 6) in the valve plate 1% to preclude the passage of air outwardly therethrough on the compression stroke of the piston 42.

Upon movement or" the piston 42 to the left, as seen in FIG. 3 of the drawings, the flapper valve 120 on the right-hand valve assembly 94 deflects to the left, as seen in FIG. 3 of the drawings, due to a pressure differential created thereacross, whereupon air is admitted through the apertures 13%} and 132 in the valve plate 106 thereof.

This movement of the piston 42 within the cylinder 40, as seen in FIG. 3 of the drawings, effects movement of the flapper valve 126 on the left-hand valve assembly 94 against the valve plate 1% thereof by the air pressure acting thereagainst and by its own resilience, sealing the apertures 13% and 132 in the left-hand valve plate 106. The disc valve 112 of the left-hand valve assembly 94 is biased against the edge portion 11 on the sleeve 11% thereof, permitting the discharge of air under pressure outwardly through the central apertures 12?. and 113 in the flapper valve 126 and valve plate 166, respectively, around the disc valve 112, through the apertures 116 in the sleeve 110 and outwardly of the valve housing 106 on the lefthand valve assembly 94.

It should be apparent that the use of like valve assemblics 94 on opposite ends 96 and 93 of the cylinder 46 results in double-action air compression in that air is compressed upon movement of the piston 42 in either direction.

From the foregoing description, it should be apparent that the air compressor of the instant invention is a relatively simple and inexpensive reciprocating compressor for pumping air or other fluids under pressure A doubleacting piston or shuttle, molded from nylon, fluorocarbon or similar plastics material, reciprocates in a complementary cylinder under the influence of a crank pin that is attached directly to the output shaft of an electric motor in eccentric relation to the central axis thereof. The screw which secures the crank pin to the output shaft of the motor acts as a balance weight for the movable component of the air compressor by the disposition of the mass of its head in opposition to the crank pin. The outer end of the crank pin engages a parallel-sided groove in the piston whereby rotation of the crank pin with the motor output shaft and about the central axis thereof effects reciprocation of the piston in the manner of a Scotch yoke.

Compression of the working fluid occurs twice per revolution as the outer faces of the piston move in turn to the outer dead center positions, i.e., in close proximity to valve assemblies at opposite ends of the cylinder. To prevent any tendency for the piston to rotate about its longitudinal axis, a spring clip is fitted over the outside of the cylinder, inwardly extending tabs on the ends thereof passing through two small holes in the cylinder and contacting a plane surface molded into the back face of the piston.

Each valve assembly contains a delivery valve and an inlet valve. The disc or delivery valve comprises a square flat plate of nylon or similar material which, during the intake stroke, seals against a circular hole in the center of a valve plate. During the exhaust stroke, the disc valve is moved outwardly against a complementary seat on a valve sleeve whereupon the compressed fluid flows around the disc valve and outwardly of a valve housing by way of holes in the valve sleeve.

The inlet valve comprises, for example, a disc of thin sheet nylon, or similar flexible material, which, during the exhaust stroke, is held sealabiy against the valve plate. During the intake stroke, the depression inside the cylinder causes the nylon flapper to flex away from the valve plate in two unsupported areas, maximum movement occurring at right angles to the center line of the support therefor. The working fluid flows into the cylinder through two elongated ports in the valve plate.

The air compressor features simple construction and the us of inexpensive manufacturing methods. The expense of a conventional machined connecting rod and Wrist pin is eliminated by fixing the crank pin directly to the output shaft of a motor and directly driving the piston thereby.

The use of nylon, fluorocarbon or other plastics material reduces and, in certain conditions, eliminates the need for fluid lubrication.

The design and position of the valve assemblies contribute substantially to cooling of the cylinder in that the flow of air or other working fluid is adjacent the cylinder wall upon passage into the cylinder. Also, simple inertia forces acting on the movable components are counterbalanced by the mass of the screw head used to secure the crank pin to the output shaft of the motor.

It is to be understood that the specified construction of the improved compressor herein disclosed and described is presented for the purpose of explanation and illustration and is not intended to indicate limits of the invention, the scope of which is defined by the following claims.

What is claimed is:

1. In combination with an electric motor having an out put shaft, a positive displacement piston-type air compres sor comprising a cylinder,

an intake valve at each end of said cylinder,

an exhaust valve at each end of said cylinder,

a molded nylon piston in said cylinder having a transverse groove therein,

a crank pin secured directly to the output shaft of said electric motor and drivably engaged in the groove in said piston thereby to effect reciprocation of said piston and alternate compression and induction of air in each end of the cylinder upon rotation of the output shaft of said motor; and

means for securing said crankpin to the output shaft of the electric motor comprising a machine screw extending through the output shaft thereof having a relatively large head on the opposite side of the output shaft from said crankpin to effect balancing thereof.

2. In combination with an electric motor having an output shaft, a positive displacement piston-type air compressor comprising a cylinder,

an intake valve at each end of said cylinder,

an exhaust valve at each end of said cylinder,

a piston in said cylinder having a transverse groove therein,

a crank pin secured directly to the output shaft of said electric motor and drivably engaged in the groove in said piston thereby to effect reciprocation of said piston and alternate compression and induction of air in each end of the cylinder upon rotation of the output shaft of said motor, and

means engageable with said cylinder and said piston for precluding rotation of said piston about its longitudinal axis comprising a longitudinal slot in said piston and a radially inwardly extending portion on said cylinder complementary to said slot.

References Cited in the file of this patent UNITED STATES PATENTS 2,472,647 Covins June 7, 1949 2,514,223 Covins July 4, 1950 FOREIGN PATENTS 220,073 Great Britain Aug. 11, 1924 

1. IN COMBINATION WITH AN ELECTRIC MOTOR HAVING AN OUTPUT SHAFT, A POSITIVE DISPLACEMENT PISTON-TYPE AIR COMPRESSOR COMPRISING A CYLINDER, AN INTAKE VALVE AT EACH END OF SAID CYLINDER, AN EXHAUST VALVE AT EACH END OF SAID CYLINDER, A MOLDED NYLON PISTON IN SAID CYLINDER HAVING A TRANSVERSE GROOVE THEREIN, A CRANK PIN SECURED DIRECTLY TO THE OUTPUT SHAFT OF SAID ELECTRIC MOTOR AND DRIVABLY ENGAGED IN THE GROOVE IN SAID PISTON THEREBY TO EFFECT RECIPROCATION OF SAID PISTON AND ALTERNATE COMPRESSION AND INDUCTION OF AIR IN EACH END OF THE CYLINDER UPON ROTATION OF THE OUTPUT SHAFT OF SAID MOTOR; AND MEANS FOR SECURING SAID CRANKPIN TO THE OUTPUT SHAFT OF THE ELECTRIC MOTOR COMPRISING A MACHINE SCREW EXTENDING THROUGH THE OUTPUT SHAFT THEREOF HAVING A RELATIVELY LARGE HEAD ON THE OPPOSITE SIDE OF THE OUTPUT SHAFT FROM SAID CRANKPIN TO EFFECT BALANCING THEREOF. 